Technical Field
Embodiments described herein relate to the field of graphical information processing and more particularly, to dynamically adjusting the frame refresh rate of a display.
Description of the Related Art
Part of the operation of many computer systems, including portable digital devices such as mobile phones, notebook computers and the like, is to employ a display device, such as a liquid crystal display (LCD), to display images, video information/streams, and data. Accordingly, these systems typically incorporate functionality for generating images and data, including video information, which are subsequently output to the display device. Such devices typically include video graphics circuitry (i.e., a display pipeline) to process images and video information for subsequent display.
In digital imaging, the smallest item of information in an image is called a “picture element,” more generally referred to as a “pixel.” For convenience, pixels are generally arranged in a regular two-dimensional grid. By using such an arrangement, many common operations can be implemented by uniformly applying the same operation to each pixel independently. Since each pixel is an elemental part of a digital image, a greater number of pixels can provide a more accurate representation of the digital image. To represent a specific color on an electronic display, each pixel may have three values, one each for the amounts of red, green, and blue present in the desired color. Some formats for electronic displays may also include a fourth value, called alpha, which represents the transparency of the pixel. This format is commonly referred to as ARGB or RGBA. Another format for representing pixel color is YCbCr, where Y corresponds to the luma, or brightness, of a pixel and Cb and Cr correspond to two color-difference chrominance components, representing the blue-difference (Cb) and red-difference (Cr).
Most images and video information displayed on display devices such as LCD screens are interpreted as a succession of ordered image frames, or frames for short. While generally a frame is one of the many still images that make up a complete moving picture or video stream, a frame can also be interpreted more broadly as simply a still image displayed on a digital (discrete or progressive scan) display. A frame typically consists of a specified number of pixels according to the resolution of the image/video frame. Most graphics systems use memories (commonly referred to as “frame buffers”) to store the pixels for image and video frame information. The information in a frame buffer typically consists of color values for every pixel to be displayed on the screen.
A constant interval between images allows a video stream or animated image to appear to move smoothly. Without a constant interval, movement of objects and people in the video stream would appear erratic and unnatural. Before the use of LCD displays and digital video standards became common, analog cathode ray tube televisions and monitors used a signal called the Vertical Blanking Interval (VBI) to re-position the electron gun from the bottom right corner of the screen back to the top left where each video frame began. The VBI signal has continued to be present in modern video systems even though its original purpose is obsolete, and it can provide a constant interval for updating image frames.
For portable digital devices employing a display device, it is challenging to determine how to drive the display device while at the same time minimizing power consumption so as to maximize the battery life of the portable device. Therefore, new techniques for providing a positive viewing experience to the user while simultaneously minimizing power consumption are desired.